Alignment devices and methods

ABSTRACT

Embodiments of the invention include devices and methods for implanting arthroplasty devices. Some embodiments include designs that allow for use of x-ray images as the only images used to fully and accurately preoperatively and intraoperatively size and align arthroplasty device components and prepare all necessary tissue.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the full benefit of U.S.Provisional Patent Application No. 61/715,631, filed Oct. 18, 2012. Theentirety of U.S. Provisional Patent Application No. 61/715,631 isincorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to the installation oforthopedic implants with respect to patient physiology and function, andparticularly to joint alignment and balancing devices and methods forarthroplasty implants.

A common source of early wear and revision of orthopedic implants isimproper alignment of the orthopedic implants relative to the naturalphysiology of the patient. Over the years, many sophisticated machinesand instruments have been tried to improve alignment of orthopedicimplants. However, many of these machines and instruments are expensiveand have not been readily adopted. For example, computer assistedsurgery (“CAS”) provides highly accurate tracking of implant andanatomic structures and provides exceptional three-dimensional models.The CAS machines and software, as well as maintenance, can be asignificant capital expenses to healthcare providers, which may or maynot be reimbursed. Also, pre-operative three-dimensional models arc notalways particularly useful to a surgeon where the surgeon is more likelyto have only x-ray (radiograph) equipment available to assist withevaluation of the surgery. MRI scans or CT scans simply often may not beavailable. The volume and format of information provided by some of themore sophisticated tools may, in fact, have a negative effect onsurgical efficiency and efficacy. Many arthroplasty instruments haverelied on penetration of the medullary canal of the bone to whichimplant components are to be attached to achieve alignment. However,penetration of the medullary canal can lead to some complications, andavoiding the practice may benefit some patients.

Improved devices and methods may rely on less expensive, more common,and more reliable imaging solutions such as a radiograph. Improveddevices may provide the right amount of useful information wheninformation is needed and in ways that are complementary to currentsurgeon preferences and practices. It may also be useful to providesurgeons with preoperative information in the same format that they canexpect to receive information intraoperatively. Similarly, postoperativeinformation provided in a like format may assist surgeons with moreaccurate evaluations of the operations performed. Providing informationthat is useful in simplifying complex decisions that are dependent onvariable inputs and factors may also be beneficial. It may also bebeneficial to provide patient-matched (“PM”) instruments that have beengenerated through the use of radiographs rather than through more costlyand less available imaging devices. Improved instruments may alsoachieve physiologically appropriate alignment without penetrating themedullary canal.

SUMMARY OF THE INVENTION

In one general aspect, an alignment guide for implanting an implantcomponent in a patient includes a body for alignment with respect to abone of the patient. The body includes an aperture extending at an anglerelative to an axis, and an offset portion configured to intersect aplane that extends through a physiological reference on the bone whenthe body is aligned with respect to the axis.

An embodiment of the invention is a femoral implant alignment guide forimplanting a femoral component in a patient. The femoral implantalignment guide may include a body configured to be placed on a distalend of a femur and be aligned on an axis from between the patient'sfemoral condyles through the patient's hip center. The body of the guidemay also include an elongated resection aperture with a major axissubstantially perpendicular to the axis through the patient's hip centerwhen the body is aligned on the axis through the patient's hip center,and an offset portion containing a slot or hole that is configured toextend to a point in a coronal plane of the patient that is shared withthe patient's greater trochanter. This point may be directly lateral ofthe patient's greater trochanter. The offset portion in some embodimentsis coupled to the body such that the body and the offset portion aresubstantially constrained from rotational displacement in coronal and/orsagittal planes of the patient.

Another embodiment of the invention is a method of manufacturing afemoral implant alignment guide configured to be used with a particularpatient. The embodiment includes evaluating one or more images of thepatient's anatomy that include the patient's hip and the patient's kneeand defining an axis from between the patient's femoral condyles throughthe patient's hip center. The method may also include forming apatient-matched body that includes an elongated resection aperture thatwhen placed against the patient's femoral condyles includes a major axisthat is substantially perpendicular to the axis from between thepatient's femoral condyles through the patient's hip center.

Still another embodiment of the invention is a method of implanting anarthroplasty device that includes providing a first instrument foraligning a first component of the arthroplasty device, wherein the firstinstrument includes an offset portion that is configured to extend to aphysiological reference point that provides an alignment reference forplacement of the first component. The method may also include aligningthe first instrument with two or more physiological reference points andremoving tissue adjacent to the first instrument to prepare a locationto receive the first component. The method may also include providing asecond instrument for aligning a second component of the arthroplastydevice, wherein the second instrument includes an interface configuredto couple with the location prepared to receive the first component, andaligning the second instrument with the location prepared to receive thefirst component. The method may include positioning tissue adjacent tothe second instrument such that tissue adjacent to the first instrumentis positioned appropriately relative to the tissue adjacent to thesecond instrument, removing tissue adjacent to the second instrument toprepare a location to receive the second component, implanting the firstcomponent of the arthroplasty device, and implanting the secondcomponent of the arthroplasty device.

Another embodiment of the invention is a method of implanting a kneearthroplasty device in a patient that includes provision of a femoralimplant alignment guide for implanting a femoral component of the kneearthroplasty device in a patient comprising a body configured to beplaced on a distal end of a femur and defining an axis from between thepatient's femoral condyles through the patient's hip center. The bodymay include an elongated resection aperture with a major axis that issubstantially perpendicular to the axis directed through the patient'ship center when the body is aligned on the axis through the patient'ship center, and an offset portion that is configured to extend to apoint in a coronal plane of the patient that is shared with thepatient's greater trochanter wherein the point is directly lateral ofthe patient's greater trochanter and wherein the offset portion iscoupled to the body such that the body and the offset portion aresubstantially constrained from rotational displacement in a coronaland/or sagittal plane of the patient. The method may also includealigning the femoral implant alignment guide with two or morephysiological reference points and removing at least a portion of thefemoral condyles along a plane defined by the elongated resectionaperture. The method also includes provision of a tibial implantalignment guide for aligning a tibial component of the knee arthroplastydevice, wherein the tibial implant alignment guide includes an interfaceconfigured to couple with the patient's femur. The method may alsoinclude aligning and coupling the tibial implant alignment guide withthe patient's femur, positioning the patient's tibia appropriatelyrelative to the patient's femur and coupling the tibial implantalignment guide to the patient's tibia, removing at least a portion ofthe patient's tibia in a configuration to receive a tibial component ofthe knee arthroplasty device, implanting a femoral component of the kneearthroplasty device, and implanting a tibial component of the kneearthroplasty device.

Yet another embodiment of the invention is a method of implanting a kneearthroplasty device in a patient that may include imaging at least thepatient's femur and proximal tibia, defining an axis on one or moreimages from between the patient's femoral condyles through the patient'ship center, and sizing a femoral implant alignment guide based on imagesof the patient's femur such that an elongated resection aperture in thefemoral implant alignment guide has a major axis substantiallyperpendicular to the axis between the patient's femoral condyles and thepatient's hip center when the femoral implant alignment guide is placedagainst the patient's femoral condyles. The method may also includealigning an offset portion of the femoral implant alignment guide with apoint in a coronal plane of the patient that is shared with thepatient's greater trochanter, wherein the point is directly lateral ofthe patient's greater trochanter, and aligning the femoral implantalignment guide with one or more physiological reference points on thedistal femur. The method may include removing at least a portion of thefemoral condyles along a plane defined by the elongated resectionaperture, coupling a tibial implant alignment guide to the patient'sfemur at least in part where at least a portion of the femoral condyleswere removed, positioning the patient's tibia appropriately relative tothe patient's femur and coupling the tibial implant alignment guide tothe patient's tibia, and removing at least a portion of the patient'stibia in a configuration to receive a tibial component of the kneearthroplasty device. The method may also include implanting a femoralcomponent of the knee arthroplasty device and a tibial component of theknee arthroplasty device.

An additional embodiment of the invention is a method of providinginformation useful for implanting an orthopedic implant that includesproviding a patient-matched instrument that includes a sensor formeasuring force applied to the patient-matched instrument, placing thepatient-matched instrument between two or more of: orthopedicinstruments, orthopedic implant components, and bones, and readingforces and/or locations of forces applied during the alignment of two ormore orthopedic instruments, orthopedic implant components, and bones.The method may also include the re-zeroing of the force sensor output ina particular patient-specific loading condition, altering the shapes oralignment of one or more orthopedic instruments, implant components andbones or other tissue, evaluating the change in the force sensor output,accepting the measured force delta or altering one or more of theorthopedic instrument, orthopedic implant components, and bones or othertissue to alter the measured force delta.

An additional embodiment of the invention is the representation of allpre-op plan information used to design the PM instrument and predictalignment outcomes within the context of one or more pre-operativeradiographs. This radiographic preoperative plan is also used as averification tool when overlaid over or otherwise compared with thepostoperative radiograph.

Further areas of applicability of the invention will become apparentfrom the detailed description provided hereinafter. It should beunderstood that the detailed description and specific examples, whileindicating the particular embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are incorporated in and form a part of thespecification, illustrate the embodiments of the invention, and togetherwith the written description serve to explain the principles,characteristics, and features of the invention. In the drawings:

FIG. 1 is an anterior to posterior radiograph of a patient's femur, hip,and knee.

FIG. 2 is an anterior to posterior radiograph of a patient's knee.

FIG. 3A is front elevation view of a femoral component of a kneearthroplasty device.

FIG. 3B is a front elevation view of a femoral implant alignment guide.

FIG. 3C is a posterior view of the femoral implant alignment guide.

FIG. 4 is a sagittal plane radiograph of a patient's knee.

FIG. 5 is a perspective view of a distal portion of a femur in a femoralimplant alignment guide.

FIG. 6 is a perspective view of a femoral implant alignment guide.

FIG. 7 is a front elevation view of a femur engaged with a femoralimplant alignment guide.

FIG. 8 is side elevation view of a femur engaged with a femoral implantalignment guide.

FIG. 9 is a top plan view of a distal portion of a femur in a femoralimplant alignment guide.

FIG. 10 is a bottom plan view of a distal portion of a femur in afemoral implant alignment guide.

FIG. 11 is a perspective view of a partially resected distal portion ofa femur.

FIG. 12 is a perspective view of a tibial implant alignment guide.

FIG. 13A is a view of the representations of portions of a femur thathave been resected derived from a sagittal radiograph of the femur priorto resection.

FIG. 13B is a view of the representations of portions of a femur thathave been resected derived from a coronal radiograph of the femur priorto resection.

FIGS. 14A and 14B are perspective views of representations of portionsof a femur that have been resected derived from sagittal and coronalviews of the femur prior to resection.

FIGS. 14C and 14D are plan views of representations of portions of afemur that have been resected showing orientations and sizes of theresected portions of the femur prior to resection.

FIG. 15A is an anterior elevation view of an instrument derived from thesize and shape of the resected portions of the femur illustrated inFIGS. 13B and 14B.

FIG. 15B is an anterior elevation view of the instrument of FIG. 15Ashown having a variety of medial and lateral offset surfaces.

FIG. 15C is an anterior elevation view of a modular embodiment of theinstrument of FIG. 15B.

FIG. 15D is an exploded view of the modular instrument of 15C.

FIG. 15E is a series of views of an alternative embodiment of theinstrument of FIG. 15A and a portable force sensor and output display.

FIG. 16A is a side elevation view of an alternative embodiment of theinstrument of FIG. 15 between a tibia and femur where the tibia isunable to achieve full terminal extension.

FIG. 16B is a side elevation view of a portion of a tibial implantalignment guide between a tibia and a femur in full terminal extension.

FIG. 16C is a frontal elevation view of the instrument of FIG. 16Bbetween a tibia and femur where the tibia is coronally misaligned andillustrates the establishment of a patient-specific load and balancedatum.

FIG. 16D is a frontal elevation view of the instrument of FIG. 16Bbetween a tibia and femur where the tibia is coronally aligned after analteration of the instrument shape.

FIG. 16E illustrates a detected load and balance change relative to thepatient-specific load and balance datum.

FIG. 17 is a perspective view of a tibial implant alignment guidebetween a tibia and a femur in full extension.

FIG. 18 is a perspective view of an instrument that includes a sensor.

FIG. 19 is a perspective view of a distal portion of a femur to which aninstrument of FIG. 18 has been coupled.

FIG. 20 is a frontal elevation view of a preoperative radiograph havingan aligned representation of the femoral implant overlaid in preparationfor comparison with the postoperative radiograph of the implantedfemoral implant.

FIG. 21 is a sagittal elevation view of a preoperative radiograph havingan aligned representation of the femoral implant overlaid in preparationfor comparison with the postoperative radiograph of the implantedfemoral implant.

FIGS. 22A-22C are a series of coronal radiographs showing undeformedalignment, deformed alignment, and restored alignment.

FIG. 23 is a distal end view of a femoral alignment guide engaged with afemur.

FIGS. 24 is a side view of the femoral alignment guide and femur of FIG.23.

FIG. 25 is a perspective view of the femoral alignment guide of FIG. 23.

FIGS. 26-28 are perspective views of the femoral alignment guide andfemur of FIG. 23 with a second guide.

FIG. 29 is a side view of the femoral alignment guide and femur of FIG.23, with the second guide of FIGS. 26-28.

FIG. 30 is a side view of the femoral alignment guide of FIG. 23 withthe second guide of FIGS. 26-28.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following descriptions of the depicted embodiments are merelyexemplary in nature and are in no way intended to limit the invention,its application, or uses.

An anterior to posterior radiograph of a patient's femur 1, hip 3, andknee 5 is shown in FIG. 1. FIG. 2 shows the patient's femur 1, knee 5,and tibia 2. The images provided in FIGS. 1 and 2 arc radiograph imagesproduced with x-rays. In some embodiments, other imaging techniques anddevices may be used, but in this embodiment, radiograph images are usedto capture preoperative information for the manufacture of an alignmentguide and for comparison with postoperative alignment information. Anaxis 10 is illustrated in FIGS. 1 and 2 that passes between thepatient's femoral condyles 4 and through the patient's hip center 11(FIG. 1). This axis 10 is well-known to approximate an appropriatealignment for a knee arthroplasty device. An axis 12 is illustrated inFIG. 2 that is substantially perpendicular to the axis 10. This axis 12provides a preoperative or intraoperative guide for instruments andimplants that may be placed on or parallel with the axis 12. The axis 12also provides an appropriate orientation for rotation of a kneearthroplasty device such that forces through the patient's knee may bemaintained along the axis 10 without generating unwanted forceeccentricities.

A femoral implant alignment guide 100 is illustrated in FIGS. 3B, 3C and5-10. The femoral implant alignment guide 100 in the illustratedembodiment is for implanting a femoral component of a total kneearthroplasty device in a patient. While this embodiment is directed to aknee arthroplasty device, in other embodiments instruments for aligningother types of arthroplasty and orthopedic devices are alsocontemplated. For example and without limitation, instruments forimplanting hip, shoulder, spine, and other devices having alteredattachment mechanisms and sizing but similar structure or function arecontemplated. The femoral implant alignment guide 100 includes a body101 and an offset portion 103. The body 101 is configured to be placedon a distal end of a femur 1 (FIGS. 5 and 7-10) and to be aligned on theaxis 10 (FIGS. 3C and 7) from between the patient's femoral condyles 4(FIGS. 1 and 9) through the patient's hip center 11 (FIGS. 1 and 7).

The axis 12 is also illustrated in FIGS. 3A and 3C substantiallyperpendicular to the axis 10 and providing an alignment reference for afemoral component 200 of a knee arthroplasty device. An elongatedresection aperture 112 is illustrated in FIGS. 3B, 3C, 5-7, and 9. Theelongated resection aperture 112 is illustrated in FIGS. 3C and 7 with amajor axis substantially perpendicular to the axis 10 through thepatient's hip center 11 (FIG. 7). As illustrated, the body 100 isaligned on the axis 10 through the patient's hip center 11. Thisconfiguration may be represented in another way by stating that theelongate resection aperture 112 has a major axis substantiallyperpendicular to a minor axis of the body 100, or may be defined withreference to any edge or surface of the body 100. As illustrated inFIGS. 2, 3A, and 3C, the relationship between alignment and the distalfemur condylar contact surfaces 14 is the same for the radiograph,implant and guide.

The hip center is commonly used to define the proximal of two points(proximal and distal) required to define the mechanical axis of thefemur, though other landmarks could be used. The distal mechanical pointlies between the femoral condyles in the coronal plane and can bedefined using any of several landmarks visible in a substantiallyanterior-posterior radiograph, for example: the most distal apex of thetrochlear groove or the medial-lateral center of the distal femur. Thedistal mechanical point lies along the femoral distal trochlear groovein the sagittal plane and can be defined using a substantially distalpoint along the distal trochlear groove which is visible in asubstantially medial-lateral radiograph.

A medial to lateral radiograph of a patient's knee is illustrated inFIG. 4 and includes markers 21, 22, 23, 24. An anterior to posteriorradiograph of a patient's knee is illustrated in FIG. 2 and includesmarkers 14. The markers 14, 21, 22, 23, 24 indicate the locations ofphysiological reference points on the distal end of the femur 1. Markers14 are medial and lateral distal femur condyle points. Marker 21 is areference point for a medial anterior ridge. Marker 22 is a referencepoint for a lateral anterior ridge. Marker 23 is a reference point for amedial posterior condyle. Marker 24 is a reference point for a lateralposterior condyle. In some embodiments, reference points such as thesemay be used to generate a patient-matched instrument or be correlatedwith an appropriate size and fit from a set of instruments to assistwith alignment of the instrument, and consequently, alignment of animplant. The markers 14, 21, 22, 23, 24 in the illustrated embodiment,are correlated with instrument size and shape references 14, 121, 122,123, 124 in FIG. 6 and apertures 109, 111 in FIGS. 6 and 10. In somecases, these markers could be correlated to functional aspects of theknee joint, such as the Q-angle by calculating the amount of femurrotation which occurs between at least two radiographs where at leastone radiograph is taken in flexion and at least one radiograph inextension. In the example shown in FIGS. 5-6, the femoral implantalignment guide 100 is a patient-matched body that includes an elongatedresection aperture 112 that when placed against the patient's femoralcondyles includes a major axis that is substantially perpendicular tothe axis 10 (FIG. 5) from between the patient's femoral condyles throughthe patient's hip center. Another type of reference point alignment isillustrated in FIGS. 9-10. As shown in this embodiment, the femur 1 maybe visually aligned through the window 127 relative to the femoralimplant alignment guide 100. This gives a surgeon options with regard toaligning as preoperative planned or making modificationsintraoperatively. It is contemplated that the femoral implant alignmentguide may be aligned with these or any other effective physiologicalreference points on the femur 1.

The offset portion 103 in the illustrated embodiment is configured toextend to a point in a coronal plane of the patient that is shared withthe patient's greater trochanter. As illustrated in FIGS. 7-8, thispoint is directly lateral of the patient's greater trochanter 7. Theoffset portion 103 shown, in addition to the portion coupled to the body101, includes a slot 104 (FIGS. 9-10) and a rod 105 (FIG. 7). The rod105 is configured to engage in the slot 104. In most cases, the greatertrochanter 7 can be assumed to adequately approximate a patient's hipcenter in a sagittal view, or an offset can be measuredradiographically. Thus, the greater trochanter 7 can be used as apreoperatively visible and intraoperatively accessible surrogate for thehip center for the purpose of sagittal alignment. Because the rod 105 isable to pivot or translate in the slot 104, the variations in softtissue thickness between the greater trochanter 7 and the skin can beaccounted for intraoperatively without affecting the sagittal positionof the rod 105 or the coronal alignment of the guide. In the sagittalplane, the relationship between the alignment guide 100 and distalmechanical point in the sagittal plan is preoperatively designed andintraoperatively constrained by references 121, 122, 123, 124. Therelationship between the alignment guide 100 and the proximal mechanicalpoint in the coronal plane is preoperatively designed andintraoperatively constrained by the rod 105, length of the needle 106from tip to rod interface, and distance between the most lateral pointof the greater trochanter and the proximal mechanical point, commonlydefined by the hip center. The relationship between the alignment guide100 and the proximal mechanical point in the sagittal plane ispreoperatively designed and intraoperatively constrained by thesubstantial perpendicularity of the rod 105 to the elongated resectionaperture 112, the substantially medial-lateral orientation of the needle106, and the distance between the most lateral point of the greatertrochanter and the proximal mechanical point in the sagittal plane whichcan be measured in a substantially medial-lateral radiograph orcorrelated to the patient type (height, sex, ethnicity, etc.) or assumedto be a constant across all patients. The sum of the designed andconstrained relationships in the sagittal plane allows theintraoperatively constrained alignment between the elongated resectionaperture 112 and mechanical axis of the femur (FIG. 22) to besubstantially similar to the preoperatively planned alignment. Thus, thegreater trochanter 7 can be used as a preoperatively visible andintraoperatively accessible surrogate for the proximal mechanical pointfor the purpose of sagittal alignment.

The offset portion 103 can include a cylindrical bore (shown in dashedline in FIG. 9) rather than a slot 104, such that the rod 105 isadditionally constrained in the coronal plane. In the coronal view, anoffset between the hip center and the most lateral point of the greatertrochanter is measureable using an anterior-posterior radiograph (FIG.7). Also in the coronal view, an offset between the most lateral pointof the greater trochanter 7 and the skin is measureable using ananterior-posterior radiograph. Both measured offsets can factor intocoronal alignment of an alignment guide 100, rod 105 and needle 106. Theaforementioned trochanter to skin offset is intraoperatively bridged byinsertion of the needle 106 through the skin until the tip contacts thelater point of the greater trochanter. The needle 106 is joinedproximally to the rod proximally near the location of the greatertrochanter and has a controlled length from tip to rod interface whichis designed to ensure that the tip of the needle can reach the greatertrochanter while maintaining its connection to the rod. At least thefollowing medial-lateral distances are used to ensure the design of thealignment guide 100, rod 105 and needle 106 result in the alignment ofthe elongated resection aperture to the femur mechanical axis in thecoronal plane: the designed distance between the distal mechanical pointand the alignment guide 100/distal rod 105 interface, the designeddistance between the proximal rod 105/lateral needle 106 interface andthe medial needle tip, and the measured distance between the mostlateral point of the greater trochanter and the proximal mechanicalpoint. The relationship between the alignment guide 100 and the distalmechanical point in the coronal plane is preoperatively designed to beintraoperatively constrained by tabs 107. The sum of the designed andconstrained relationships in the coronal and sagittal planes allows theintraoperatively constrained relationship between the elongatedresection aperture 112 and mechanical axis of the femur (FIG. 22) to besubstantially similar to the preoperatively planned relationship. Thus,the greater trochanter 7 can be used as a preoperatively visible andintraoperatively accessible surrogate for the hip center for the purposeof sagittal and coronal alignment.

In order to facilitate the surgeon's fine-tuned placement of the needletip, the rod may be preoperatively designed to a length consistent withthe distance between distal and proximal mechanical points of the femur.In order to limit error in the position of the needle tip, the rotationof the rod about its axis is constrained such that the needle points ina substantially medial-lateral direction.

The femoral implant alignment guide 100 can include tabs 107 (FIGS. 5and 6) for constraining medial/lateral position of the guide 100 to apreoperatively defined position relative to the distal femur 1. The tabs107 are spaced based on x-ray measures and can be made flexible toaccommodate a tighter fit or possible error in the x-ray measurement.

The relationships between coronal alignment of some apertures 112, 1001,1002 and distal femur condylar contact surfaces 14 are isomorphic withthe relationships between the femur coronal alignment and the mostdistal femur medial and lateral condylar points 14. The relationshipsbetween the rotational alignment of some apertures 109, 111 and themedial and lateral anterior femoral ridges contact surfaces 121, 122 areisomorphic with the relationship between the leading medial and lateralanterior femoral ridges 21, 22 and the Q-angle as calculated by theinferred rotation of the femur occurring between extension and flexionas measured by at least two lateral x-rays. The relationships betweenthe rotational alignment of some apertures 109, 111 and the medial andlateral posterior femoral condylar contact surfaces 123, 124 areisomorphic with the relationship between the medial and lateralposterior femoral condylar tangencies 23, 24. The relationship betweenthe medial-lateral position of some apertures 112, 1001, 1002, 109, 111and the medial and/or lateral constraining surfaces 107 is isomorphicwith the medial to lateral width of the distal femur 1003.

A partially resected distal portion of a femur 1 is shown in FIG. 11.Connection holes 40 have been prepared through the resected distalportion of the femur 1. A tibial implant alignment guide 300 isillustrated in FIG. 12. Interface pins 340 that arc configured to couplewith connection holes 40 are also depicted. The tibial implant alignmentguide 300 is a known device that is disclosed in detail in U.S. Prov.Pat. Appl. Ser. Nos. 61/681,475 and 61/715,462, both entitledPATIENT-MATCHED TOTAL KNEE ARTHROPLASTY, and filed on Aug. 21, 2012 andOct. 18, 2012 respectively, each of which is hereby incorporated byreference in its entirety.

In general, the tibial implant alignment guide 300 includes a distalfemur gauge including medial and lateral condyle paddles 312, 314 eachhaving a shape and size corresponding to a pre-operative planned distalresection of a patient's femur. In this case, the resections correspondto the tissue removed from the femur illustrated in FIG. 11. The tibialimplant alignment guide 300 shown also includes a cutting blockcomponent with an elongated resection aperture 322. When the tibialimplant alignment guide 300 is coupled with the femur 1 and thepositions of the patient's tibia and femur are brought into appropriaterelative positions, a portion of the patient's tibia can be resected sothat a tibial component of a knee arthroplasty device can be accuratelyplaced. More particularly regarding determining appropriate fit when thetibia and femur are in appropriate relative positions, a surgeon may putthe leg in extension and place the distal-facing surfaces of the condylepaddles 312, 314 against the native tibia, as similarly illustrated inFIG. 16B. If the limb cannot return to full extension (i.e. flexioncontracture FIG. 16A), then this indicates that too little distal femurhas been resected. By how much the distal femur has been under resectedcan be gauged by simulating a distal femur recut through removingthickness from the distal femur gauge in increments of 1 mm, asdescribed in US Published Application No. 2010/0305575, titled Methodand Apparatus for Performing Knee Arthroplasty, hereby incorporated byreference in its entirety. It has been found that 1 mm of distal femurgauge thickness reduction will allow between 1 and 2 degrees ofadditional extension. If instead of flexion contracture, the limbexhibits hyperextension, this indicates that too much distal femur hasbeen resected. Material can then be added to the thickness of thecondyle paddles in 1 mm increments resulting in 1-2 degrees of reducedextension. In this way one can gauge exactly how much the distal femurhas been under or over resected relative to the native joint line asrepresented by the native tibial articular geometry. This information isuseful as it can directly or indirectly affect subsequent decisions andoutcomes.

FIGS. 14A and 14B illustrate representations of portions of a femur thathave been resected. The illustrated shapes were derived from sagittal(FIG. 13A) and coronal (FIG. 13B) views of the femur prior to resection,and consequently, are consistent with information that can be obtainedfrom standard radiographic images. CAD software has been used to assistwith defining the volumetric shapes illustrated in FIG. 14B. FIGS. 14Cand 14D show representations of portions of a femur that have beenresected showing orientations and sizes of the resected portions of thefemur prior to resection. CAD software has been used to assist withdefining the likely curvatures, as shown in FIG. 14D. The orientation ofthese likely curvatures are needed for understanding how to best matchthe anatomy; however, are not visible in radiographs. Though early datashows that the orientation could mismatch as much as 10 degrees withnegligible effect on alignment, alternative sources of data (patientheight, sex, ethnicity, etc.) could be used to infer, calculate andpredict the orientation of these likely curvatures in order to minimizemismatch. These shapes arc used to derive a distal femur gauge portionof a tibial implant alignment guide 300 including medial and lateralcondyle paddles 312, 314, as illustrated in FIGS. 12 and 15A. Inclusionof the standing coronal deformity and maximum passive extension of thelimb could be included to further educate the design of the instrument.

A method embodiment of the invention is a method of manufacturing afemoral implant alignment guide, such as but not limited to, the femoralimplant alignment guide 100 configured to be used with a particularpatient. Embodiments of this method include evaluating one or moreimages of the patient's anatomy that include the patient's hip and thepatient's knee. For example, evaluating FIGS. 1 and 2. The method mayalso include defining an axis from between the patient's femoralcondyles through the patient's hip center. This definition isillustrated by the axis 10 that passes through the patient's hip center11 and between the patient's condyles 4. Another act of the embodimentis forming a patient-matched body that includes an elongated resectionaperture that when placed against the patient's femoral condylesincludes a major axis that is substantially perpendicular to the axisfrom between the patient's femoral condyles through the patient's hipcenter. The femoral implant alignment guide 100 demonstrates such apatient-matched body. The markers 21, 22, 23, 24 in the illustratedembodiment, are correlated with instrument size and shape references121, 122, 123, 124 in FIG. 6. In the example shown in FIGS. 5-6, thefemoral implant alignment guide 100 is a patient-matched body thatincludes an elongated resection aperture 112 that when placed againstthe patient's femoral condyles includes a major axis that issubstantially perpendicular to the axis 10 (FIG. 4) from between thepatient's femoral condyles through the patient's hip center.

An embodiment of the invention is a method of implanting a kneearthroplasty device in a patient. The method described herein is a totalknee arthroplasty. However, in other variations the method described isapplicable to partial knee replacements such as a unilateral kneereplacement, and may also be applicable to other arthroplastyprocedures. The femoral implant alignment guide 100 for implanting thefemoral component 200, each as has been more specifically describedherein, is provided as part of the method described. In the illustratedembodiment, the femoral implant alignment guide 100 is aligned with twoor more physiological reference points. For example as shown in FIG.7-8, the rod 105 is aligned with the greater trochanter 7 as a surrogatefor the hip center 11. This alignment controls the tilt of the femoralimplant alignment guide 100 along the sagittal plane. Similarly,alignment of the distal femur relative to the femoral implant alignmentguide 100 may be accomplished, as shown in FIGS. 9-10. Particularly, thefemur 1 may be visually aligned through the window 127 relative to thefemoral implant alignment guide 100. This gives a surgeon options withregard to aligning as preoperative planned or making modificationsintraoperatively. It is contemplated that the femoral implant alignmentguide may be aligned with these or any other effective physiologicalreference points on the femur 1.

With the femoral implant alignment guide 100 in an appropriate locationrelative to the femur 1, a saw or other cutting device may be used toremove at least a portion of the femoral condyles along the planedefined by the elongated resection aperture 112, which is illustrated inFIGS. 3B, 5-7, and 9. Depending upon the configuration of the femoralcomponent, other cuts to the femur may be necessary prior toimplantation of the femoral component. Also, in some embodiments, anextension measurement may result in recognition of the need for anadditional femoral cut. If this happens, an additional cut through thefemoral implant alignment guide 100 or a cut separate from the femoralimplant alignment guide 100 may be necessary to ensure proper fit of thearthroplasty device.

In an additional act of the method, the tibial implant alignment guide300, as illustrated in FIG. 12, is provided to assist with aligning thetibial component of the knee arthroplasty device by making anappropriate cut on the tibia 2. The tibial implant alignment guide 300includes a distal femur gauge including medial and lateral condylepaddles 312, 314. These condyle paddles 312, 314 along with theinterface pins 340, which are configured to couple with connection holes40 in the femur 1, provide an interface with the patient's femur, suchas the femur 1 illustrated in FIG. 11. Other devices and techniques foraligning and coupling the tibial implant alignment guide 300 with thepatient's femur 1 may be effective as well. For example, an alternativeembodiment for a tibial alignment guide is illustrated in use in FIG.16B. This alternative embodiment alignment guide does not include anintegrated component that provides a guide for resection of the tibia 2.However, it is useful in achieving alignment of the tibia 2 and thefemur 1.

In a further act of this method embodiment, the patient's tibia 2 isappropriately positioned relative to the patient's femur 1. Anappropriate positioning provides for recovered or corrected anatomicalalignment of the patient. An additional consideration is the balancingof soft tissues adjacent to the knee such that the joint operates witheven pressures and wear to the implant components. For the tibialimplant alignment guide 300 illustrated in FIG. 12, the condyle paddles312, 314 and their connecting components may be separated from the lowerportion of the instrument such that after an alignment is accomplishedwith the patient's leg extended, the patient's leg may be flexed priorto cutting of the tibia 2. When aligning and positioning is complete andthe tibial implant alignment guide 300 has been coupled to the tibia 2,a portion of the patient's tibia can be removed with a saw or othercutting device such that the tibia 2 is configured to receive a tibialcomponent of the knee arthroplasty device. To complete some embodimentsof the invention a femoral component, such as the femoral component 200of the knee arthroplasty device, is implanted, and a tibial component isimplanted.

Another embodiment of the invention is a method of implanting a kneearthroplasty device in a patient that contemplates acts that enable asuccessful knee arthroplasty surgery using only two-dimensional imagingtechniques. Specifically, in this method images of at least a patient'sfemur and proximal tibia are taken, as illustrated, for example, inFIGS. 1 and 2. An additional act is to define an axis on one or more ofthe images from between a patient's femoral condyles through thepatient's hip center, as demonstrated by the axis 10 in FIGS. 1, 2, 3A,and 3C.

As described in association with FIGS. 4-6 herein, another act of thepresent method is sizing the femoral implant alignment guide 100 basedon images of the patient's femur 1 such that the elongated resectionaperture 112 in the femoral implant alignment guide 100 has a major axissubstantially perpendicular to the axis 10 when the femoral implantalignment guide 100 is placed against the patient's femoral condyles.Another act of the embodiment is to align the femoral implant alignmentguide 100 with a point in a coronal plane of the patient that is sharedwith the patient's greater trochanter 7 (FIG. 7-8), the point beingdirectly lateral of the patient's greater trochanter 7. Similarly,alignment of the distal femur relative to the femoral implant alignmentguide 100 as shown in FIGS. 9-10 may be accomplished. Particularly, thefemur 1 may be visually aligned through the window 127 relative to thefemoral implant alignment guide 100. This gives a surgeon options withregard to aligning as preoperative planned or making modificationsintraoperatively. It is contemplated that the femoral implant alignmentguide may be aligned with these or any other effective physiologicalreference points on the femur 1.

FIGS. 23-29 illustrate another embodiment of the femur alignment guidedesigned preoperatively using at least radiographic information andwhich may incorporate some or all of the features of previouslydescribed embodiments. These features and some additional featuresdescribed below facilitate a method of using the guide 500 to align anelongated resection aperture 112 in superior-inferior translation,sagittal and coronal alignment as well as the anterior-posteriorposition and internal-external rotation of a pair of cylindricalapertures 109, 111 intended to guide the making of holes 40 whichtogether serve to provide bone modifications which constrain thealignment of subsequent instruments, resections and ultimately thefemoral implant.

First, the guide 500 is approximately placed on the distal femur suchthat the trochlear probe 501 points to the distal trochlear sulcus 502(FIG. 24). The guide 500 is then provisionally secured with a pin 505through an elongated tapered aperture 506 which serves to grosslyconstrain the guide 500 to the distal femur in preparation forsubsequent alignment fine tuning (FIG. 23). The shape of the elongatedtapered aperture 506 is such that it allows up to at least 15 degrees ofcoronal, sagittal, transverse rotations and 10 millimeters ofanterior-posterior translation freedom for fine-tuning.

Second, the proximal trochanter probe 510 is inserted into the skinlateral to the most lateral point of the greater trochanter 7 until thetip of the trochanter probe 510 contacts the most lateral point of thegreater trochanter 7.

Third, the rod 515 is connected to both the trochanter probe 510 and theoffset portion 103 of the guide 500 through apertures 517, 518 whichconstrain the rotation of the rod 515 about its long axis. One exampleof how rotation might be controlled is shown in FIG. 28. The rod 500might be shaped with an orientation feature 516 such as a flat regionwhich corresponds to apertures 517, 518 of the trochanter probe 510 andguide 500 which have a complementary orientation feature 519 clocked toa particular orientation.

With the system of guide 500, rod 515 and trochanter probe 510 matedtogether, and with the trochlear probe 501 pointing to the distaltrochlear sulcus 502 and the trochanter probe 510 in contact with themost lateral point of the greater trochanter 7, the alignment of theguide 500 to the distal femur 1 can be fine-tuned in anterior-posteriorposition and internal-external rotation (FIG. 24). The guide 500 may bepreoperatively configured or intraoperatively reconfigured to enableintraoperative internal-external rotation fine-tuning by removal ofeither the medial or the lateral posterior condyle contacts 123, 124(FIG. 25) by frangible or modular disconnection means for example.Removal of one or the other frees the guide 500 to rotate about thedesired posterior condyle in order to align the central window 503 ofthe guide 500 with the anterior-posterior axis 504 of the distal femur1. Alternatively, the window 503 could be used to verify acceptablealignment with the anterior-posterior axis when both posterior condylecontacts 123, 124 are functional. If both posterior condyle contacts123, 124 are removed, the surgeon may be able to freely adjust theanterior-posterior position of the guide while maintain desiredrotational alignment between the window 503 and the anterior-posterioraxis 504.

One reason a surgeon may desire to alter the anterior-posterior positionof the guide 500 would be in response to the visualization of theanterior resection through slots 508, which are configured to representthe anterior resection slot. If after visualizing the anterior resectionby placing a sawblade simulator in slots 508 and comparing to theanterior geometry of the distal femur 1 the surgeon predicts notching,the surgeon may opt to shift the guide 500 anterior by 1 to 4millimeters. Indices 509 placed along the elongated tapered aperture 506may help with measuring and controlling the amount of anterior-posterioradjustment is made (FIG. 23). Contact with the patella could impedecorrect alignment of the guide 500. An inferior offset 507 applied tothe offset portion 103 relative to the body of the guide 500 avoidscontact with the patella and associated soft tissue structures when thepatella relocated laterally during surgery.

While the relationships of the probes 501, 510 to anatomic landmarks502, 7 are maintained, coronal and sagittal alignment willsimultaneously update in response to fine-tuned translation and rotationadjustments. The resection depth reference can be pre-operativelyselected. In FIG. 24, the guide 500 has been preoperatively configuredto reference the distal trochlear sulcus 502 for setting resectiondepth, as indicated by the contact made between the trochlear probe 501and distal trochlear sulcus 502. In another embodiment the distal medialor lateral condyle might be selected as the resection depth reference.In such case, the medial or lateral condyle would be in contact with themedial contact surface 520 or lateral contact surface 521 of the guide500.

With all alignment degrees of freedom set, pins 525 are inserted intothe distal femur 1 and through apertures 109, 111 (FIG. 26). These pins525 serve to create holes 40 in the distal femur which will set therotation of the implant through subsequent steps in the TKA surgicaltechnique. These pins 525 also serve to further stabilize the guide 500.

Next, as shown in FIGS. 26 and 27, a second guide 600 is attached to theguide 500. The second guide 600 could be constructed as a single piecewith guide 500. The second guide 600 serves to guide additional pins 605using apertures 601 and could also guide a saw in the making of aresection through an elongated resection aperture 112. This resectioncould be a distal resection or an anterior resection depending on howthe second guide 600 is preoperatively configured to connect with theguide 500. The second guide 600 mates with the guide 500 such that theelongated resection aperture 112 and additional pin apertures 601 arelocated at a preoperatively selected offset from the preoperativelyselected resection reference.

With guide 500 secured to the distal femur 1 by pins 525 throughapertures 109, 111, the second guide 600 mated to the guide 500 andsecured to the distal femur 1 by pins 605 through apertures 601, theassembly, the resection can now be made through the elongated resectionaperture 112. Prior to making the resection, the surgeon may opt todisassemble some or all the assembly except for the pins 605 and secondguide 600. Alternatively, the surgeon may elect to forgo the use of thesecond guide 600 and instead elect to assemble an alternative guide topins 605.

With the femoral implant alignment guide 100 in an appropriate locationrelative to the femur 1, a saw or other cutting device may be used toremove at least a portion of the femoral condyles along the planedefined by the elongated resection aperture 112, which is illustrated inFIGS. 3B, 5-7, and 9. Depending upon the configuration of the femoralcomponent, other cuts to the femur may be necessary prior toimplantation of the femoral component. Also, in some embodiments, anextension measurement may result in recognition of the need for anadditional femoral cut. If this happens, an additional cut through thefemoral implant alignment guide 100 or separate from the femoral implantalignment guide 100 may be necessary to ensure proper fit of thearthroplasty device.

In an additional act of the method, the tibial implant alignment guide300, as illustrated in FIG. 12, is provided to assist with aligning thetibial component of the knee arthroplasty device by making anappropriate cut on the tibia 2. The tibial implant alignment guide 300includes a distal femur gauge including medial and lateral condylepaddles 312, 314. These condyle paddles 312, 314 along with theinterface pins 340, which are configured to couple with connection holes40 in the femur 1, provide an interface with the patient's femur, suchas the femur 1 illustrated in FIG. 11. Other devices and techniques foraligning and coupling the tibial implant alignment guide 300 with thepatient's femur 1 may be effective as well. For example, an alternativeembodiment for a tibial alignment guide is illustrated in use in FIG.16B. This alternative embodiment typical alignment guide does notinclude an integrated component that provides a guide for resection ofthe tibia 2. However, it is useful in achieving alignment of the tibia 2and the femur 1.

In a further act of this method embodiment, the patient's tibia 2 isappropriately positioned relative to the patient's femur 1. Anappropriate positioning provides for recovered or corrected anatomicalalignment of the patient. An additional consideration is the balancingof soft tissues adjacent to the knee joint such that the joint operateswith even pressures and wear to the implant components. For the tibialimplant alignment guide 300 illustrated in FIG. 12, the condyle paddles312, 314 and their connecting components may be separated from the lowerportion of the instrument such that after an alignment is accomplishedwith the patient's leg extended, the patient's leg may be flexed priorto cutting of the tibia 2. When aligning and positioning is complete aportion .of the patient's tibia can be removed with a saw or othercutting device such that the tibia 2 is configured to receive a tibialcomponent of the knee arthroplasty device. To complete some embodimentsof the invention a femoral component, such as the femoral component 200of the knee arthroplasty device, is implanted, and a tibial component isimplanted.

A patient-matched instrument with sensor 500 is illustrated in FIGS.18-19. This patient-matched instrument with sensor 500 is similar infunction to the distal femur gauge portion of the tibial implantalignment guide 300 illustrated in FIG. 15A, but includes additionalsensor technology. The patient-matched instrument with sensor 500 isshown coupled to the distal end of the femur 1 in FIG. 19. Thepatient-matched instrument with sensor 500 includes medial and lateralcondyle paddles 512, 514, each having a shape and size corresponding toa pre-operative planned distal resection of a patient's femur. Interfacepins 540 that are configured to couple with connection holes 40 (FIG.11) are also depicted. The condyle paddles 512, 514 are connected by abridge 535. In various embodiments, these condyle paddles 512, 514 maybe modular such that different shapes and sizes and different sensorsmay be substituted at either location. As illustrated, each of thecondyle paddles 512, 514 includes a respective sensor 532, 534. Thesensors may, without limitation, be pressure sensitive, measurelocation, or be sensitive to relative displacement. A first indicatorlight 536 and the second indicator light 537 are connected directly orthrough a logic circuit to one or both of the sensors532, 534. Inresponse to readings taken from the first indicator light 536 and thesecond indicator light 537, a user can more readily make decisionsregarding placement and orientation of bone manipulations made inpreparation for implanting an orthopedic device.

Indicator lights communicate force and/or balance and/or force locationinformation using visible or invisible means. When using visible means,this information is communicated directly to the usual visually. Whenusing invisible means, this information is communicated through aninterpretive device which can perform translation, display, storage, andtransmission tasks or merge the information with other data prior toperforming the aforementioned tasks.

A method embodiment includes providing information useful for implantingan orthopedic implant by providing a patient-matched instrument thatincludes a sensor for measuring force applied to the patient-matchedinstrument. For example, the patient matched instrument with sensor 500may include a sensor for measuring force in one or both of the sensors532, 534. As shown in FIG. 19 the patient matched instrument with sensor500 may be placed on the femur 1 where it can be placed between thefemur 1 and another bone, an orthopedic instrument, or an orthopedicimplant component (FIG. 16B). With the sensors 532, 534 in place asillustrated a method may include reading forces applied during alignmentof two or more orthopedic instruments, orthopedic implant components,and bones. Once force readings are available, and possibly displayedthrough the indicator lights 536, 537, a user may accept the measuredforces or may alter one or more of the orthopedic instruments,orthopedic implant components, and bones or other tissue to change themeasured forces.

Another method embodiment includes indicator lights which can be zeroedor normalized to particular conditions for the purpose of comparing theeffect of a relative change. For instance, beginning with a tibial guideconfigured to match the resected portions of the native distal femurcondyles, the native forces and balance in extension would be restoredand captured qualitatively or quantitatively through the aforementionedsensors imbedded within the “native” tibial guide. Native alignmentwould also be restored including any deformities in the coronal orsagittal planes (FIG. 16C). At this time, the sensors and/or indicatorlights can be zeroed relative to the “native” condition of the knee inextension as reproduced by the unaltered replica of the native distalfemur (FIG. 16C). Next, the tibia guide and/or distal femur resectioncan be reconfigured through a variety of means (FIGS. 15B-15D) tocorrect for any sagittal or coronal alignment deformities (FIG. 16D),including a transfer of the sensor from the native replica shape to thecorrected replica shape as shown in FIG. 15E. The changed involved wouldbenefit alignment at the cost of extension forces and balance (FIG. 16E,indicating an imbalance). Typically this negative effect on forces andbalance is not precisely detectable to the surgeon but only roughlydetectable through tactile perception or spacer shims. With the use ofsensors and indicators calibrated to detect the effect of the change inalignment, now the effect of alignment improvements on soft tissuegenerated forces and balance can be precisely measured, evaluated andaccounted for through informed subsequent surgical action. Thiscalibration, or zeroing of sensors relative to a patient-specific “forcedatum” alleviates at least one common problem type in TKA: the variableeffect of upper and lower limb weight on the tactile evaluation of kneeforces and balance.

Force or balance deltas with respect to the patient-specific force datumcan be communicated to the user directly through visual indicators orindirectly through either indicators visible or invisible to thesurgeon, which can be detected by an interpretive device. Thisinterpretive device can perform translation, display, storage ortransmission tasks or merge the two or more data sets prior toperforming the aforementioned tasks. Such an interpretive device canalso be equipped to visually detect the alignment of the tibia throughthe use of fiducial makers present on an alignment rod and the tibia.Such markers on the tibia can be ink marks made by the surgeonindicating anatomic landmarks or can be features of an instrument placedby the surgeon on anatomic landmarks of the tibia. By detecting bothforce and alignment information, the interpretive device is enabled toprovide a greater variety of output to the surgeon through translation,display, storage, transmission or merging two or more data sets prior tothe aforementioned tasks. By combining two or more data sets, theinterpretive device may allow for more a simplification of beneficialyet complex intraoperative decision making For instance the use ofmultiple patient matched instruments coupled with sensors calibrated topatient-specific “force datums” are considered where each instance isapplied to one of several articulating compartments of the knee jointincluding the distal femur and proximal tibia, the posterior femur andproximal tibia, the anterior femur and posterior patella. With more thanone input to consider, the interpretive device could bear the burden oftranslating inputs to decisions or recommendations through logicalprogramming.

As illustrated in FIGS. 15B-15D, the tibia guide can be reconfigured byapplying offsets to the replica(s), and the reconfigured replica(s) canbe made modular to allow for intra-operative changes or there could be afamily of single piece constructs. One or more reconfigured replicaoptions can be provided to the surgeon for intraoperative assessment andfinal decision making. These reconfigured replica options can bedesigned utilizing patient deformity information (FIG. 22B) acquiredfrom full femur and tibia radiographs taken in substantiallymedial-lateral and/or anterior-posterior orientation and/or fromfunctional assessment by the surgeon in preoperative consultation suchas maximum passive flexion/extension, coronal laxity, oranterior/posterior drawer testing. FIG. 22A illustrates an undeformedalignment where a reconfigured replica is not needed; FIG. 22Billustrates a deformed alignment; and FIG. 22C illustrates restoredalignment of the femur and tibia of FIG. 22B using a reconfiguredreplica.

Implants can be manufactured and provided intraoperatively, whichreflect the geometry of the reconfigured replicas. The implants can bedesigned or selected to optimally address the particular deformity whichnecessitated the particular reconfigured replica.

Alternative embodiments of the process of using a patient-matchedinstrument coupled with a sensor or establishing and using apatient-specific “force datum” described above for the medial and/orlateral tibia-femoral compartments in extension include applications ofthe same device or process for the medial and/or lateral tibia-femoralcompartments in particular or all degrees of flexion and extensionincluding removing and replacing distal and posterior femur condyles orproximal tibia condyles, and also for the patella-femoral (PFJ)compartment in particular or in all degrees of flexion and extensionincluding removing and replacing the anterior femur or posteriorpatellar anatomy. Application of the process of establishing and using apatient-matched instrument coupled with sensors or a patient-specific“force datum” is considered for each of the aforementioned compartmentsand anatomies individually or in combination of two or more compartmentsand/or anatomies.

FIGS. 20 and 21 illustrate preoperative plan information, including theinformation related to the design of the PM instrument and the plannedimplant placement, provided to the surgeon in the context ofpreoperative radiographs. To acquire some types of preoperativeinformation needed to correctly visually express the planned alignment,two or more radiographs may be required to allow triangulated points,axes and planes derived from landmarks of the bone to serve asreferences for aligning points, axes and planes of the implant. The tworadiographs can be taken, for example, with the patient placed indiffering orientations, particularly with at least some flexion androtation differences between radiographs. At least one preoperativeradiograph can be configured for viewing intraoperatively for referenceand post-operatively for comparison with a postoperative radiographusing conventional radiograph viewing means such as a light box.Preoperative radiographs can be configured for overlay comparison withpostoperative radiographs such that the preoperative plan informationand the postoperative result information can be directly visuallycompared using conventional radiograph viewing means. Such direct visualoverlay comparison assumes that the patient is oriented relative to thex-ray emitter in a way substantially consistent between preoperative andpostoperative radiographs. In the case when the patient is notconsistently rotated in preoperative and postoperative radiographs, morethan one postoperative radiograph can be acquired to allow fortriangulation of points, axes and planes derived from landmarks of theimplant and bone, which provide the ability to quantify the orientationor transformation between the preoperative and postoperative implantsand bones. To facilitate the comparison of preoperative andpostoperative implant to bone alignment, several approaches can betaken. One approach takes separate radiographs of the full femur andfull tibia to ensure each is oriented to the x-ray emitter consistentlybetween preoperative and postoperative radiographs. A second approachconstrains the femur, tibia or full leg with an anatomical brace eitherhaving a known orientation relative to the x-ray emitter or havingfiducial markers of a known fixed relationship to thepatient-constraining features of the brace. Such a brace constrains orprovides references for the heel to toe axis and location, the hip tohip axis and location, and the ground to tibia angle to ensureconsistent body placement when planning or evaluating alignment ofimplants. The capability of the preoperative plan to predictpostoperative results can be enhanced with additional radiographs ofdiffering yet known orientations.

Quantified preoperative and postoperative aligmnent comparisons can heprovided to a customer for purposes of tracking the amount of variationwhich exists across the span of the TKA process steps (preoperativemeasurement, planning, design, manufacture, intraoperative alignment,balance and postoperative measurement). Such data can be delivered tothe customer in a format conducive to demonstrating process control orquantifying process noise, particularly in a manner where postoperativemeasurements are described in terms of their deviation from preoperativeplanning targets. Such preoperative to postoperative radiographiccomparison feedback data can be provided to the surgeon in a variety offormats at regular intervals and could be coupled with preoperative andpostoperative physiological data, active or passive stability, balance,function, motion and pain data acquired during postoperativerehabilitation, other historical data from the patient or a pool ofpatients. Such a system of feedback loops can serve as a basis forrecommendations for improvements to preoperative planning and design,intraoperative balance and postoperative rehabilitation steps in thespan of the TKA process.

Such a system of feedback loops can be particularly useful for educatingdecisions made in preoperatively planning and intraoperative balancesteps. For example, when preoperatively planning, a surgeon can adjustpre-operative alignment targets, designs or intraoperative force orbalance deltas with respect to the patient-specific force datum based onthe effect of alignment target on rehab metrics. For another example,preoperative planning, intraoperative balancing or postoperative rehabprotocols can be adjusted to account for particular preoperativequalities for the purpose of minimizing the potential of adverse rehabmetrics. Long term outcome metrics such as survivorship and patientsatisfaction can be coupled to further educate decisions made duringsteps in the span of the TKA process.

Feedback loops can exist both between surgeries and within a surgery.Feedback loops within surgery described herein include those related tothe balance and alignment of the knee joint through the use of a patientmatched instrument coupled with a sensor and indicators capable ofestablishing a patient specific force datum and providing informationregarding the effect of alignment changes with respect to that forcedatum. This feedback loop can be enhanced using an interpretive deviceintraoperatively. In such cases, the interpretive device can facilitatenot only the intraoperative feedback loop but also an interoperative(between surgeries) feedback loop by incorporating external data toinform intraoperative balance and alignment decision criteria.

Various embodiments of a surgical instrument wholly or its componentsindividually may be made from any biocompatible material. For exampleand without limitation, biocompatiblc materials may include in whole orin part: non-reinforced polymers, reinforced polymers, metals, ceramicsand combinations of these materials. Reinforcing of polymers may beaccomplished with carbon, metal, or glass or any other effectivematerial. Examples of biocompatible polymer materials include polyamidebase resins, polyethylene, low density polyethylene,polymethylmethacrylate (PMMA), polyetheretherketone (PEEK),polyetherketoneketone (PEKK), a polymeric hydroxyethylmethacrylate(PHEMA), and polyurethane, any of which may be reinforced. Examplebiocompatible metals include stainless steel and other steel alloys,cobalt chrome alloys, tantalum, titanium, titanium alloys,titanium-nickel alloys such as Nitinol and other superelastic orshape-memory metal alloys.

Terms such as distal, proximal, medial, lateral, and the like have beenused relatively herein. However, such terms are not limited to specificcoordinate orientations, but are used to describe relative positionsreferencing particular embodiments. Such terms are not generallylimiting to the scope of the claims made herein. Any embodiment orfeature of any section, portion, or any other component shown orparticularly described in relation to various embodiments of similarsections, portions, or components herein may be interchangeably appliedto any other similar embodiment or feature shown or described herein.

As various modifications could be made to the exemplary embodiments, asdescribed above with reference to the corresponding illustrations,without departing from the scope of the invention, it is intended thatall matter contained in the foregoing description and shown in theaccompanying drawings shall be interpreted as illustrative rather thanlimiting. Thus, the breadth and scope of the invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the claims and their equivalents.

1-16. (canceled)
 17. A femoral implant alignment guide, comprising: abody configured to be placed on a distal end of a femur of a patient inalignment with an axis from between a medial condyle of the femur and alateral condyle of the femur through a hip center of the patient,wherein the body comprises: an elongated resection aperture with a majoraxis substantially perpendicular to the axis through the hip center whenthe body is placed on the distal end of the femur in alignment with theaxis through the hip center; a medial portion comprising a medial taband configured to contact the medial condyle when the body is placed onthe distal end of the femur in alignment with the axis through the hipcenter; and a lateral portion comprising a lateral tab and configured tocontact the lateral condyle when the body is placed on the distal end ofthe femur in alignment with the axis through the hip center, wherein themedial and lateral tabs are positioned on the body to constrain amedial-lateral position of the femur with respect to the body when thebody is placed on the distal end of the femur in alignment with the axisthrough the hip center.
 18. The femoral implant alignment guide of claim17, wherein the body defines an opening between the medial and lateralportions, wherein the opening extends from a posterior side of the bodyanteriorly beyond the medial and lateral tabs.
 19. The femoral implantalignment guide of claim 17, wherein the medial and lateral tabs arespaced apart by a distance corresponding to a medial-lateral width ofthe distal end of the femur.
 20. The femoral implant alignment guide ofclaim 17, further comprising an offset portion coupled to the body,wherein the offset portion is configured to extend to a point located ina coronal plane of the patient when the body is placed on the distal endof the femur in alignment with the axis through the hip center, whereinthe coronal plane is shared with a greater trochanter of the patient.21. The femoral implant alignment guide of claim 17, wherein the bodyfurther comprises patient-specific references located to contact thedistal end of the femur at two or more locations of the femur.
 22. Thefemoral implant alignment guide of claim 21, wherein the two or morelocations comprise an anterior-most point on a medial anterior portionof the femur and another anterior-most point on a lateral anteriorportion of the femur.
 23. The femoral implant alignment guide of claim17, further comprising an offset portion that is affixed to the body andextends laterally from the body beyond the femoral condyles when thebody is placed on the distal end of the femur in alignment with the axisthrough the hip center.
 24. The femoral implant alignment guide of claim17, wherein the body is shaped such that, when the distal end of thefemur is received by the body, the body extends around the medial andlateral condyles from anterior-most points on the medial and lateralcondyles toward posteriors of the medial and lateral condyles.
 25. Thefemoral implant alignment guide of claim 17, wherein the body isconfigured to simultaneously engage the medial condyle with the medialportion and the lateral condyle with the lateral portion when the bodyis placed on the distal end of the femur in alignment with the axis frombetween the femoral condyles through the hip center.
 26. The femoralimplant alignment guide of claim 17, wherein the body has an anteriorconnecting portion that connects the medial and lateral portions,wherein the medial and lateral portions each project posteriorly fromthe anterior connecting portion.
 27. The femoral implant alignment guideof claim 17, wherein the body further comprises: a medial anteriorportion contact surface configured to engage an anterior portion of themedial condyle; and a lateral anterior portion contact surfaceconfigured to engage another anterior portion of the lateral condyle,wherein the medial and lateral anterior femoral portion contact surfacesare configured to restrict anterior displacement of the body withrespect to the femur.
 28. The femoral implant alignment guide of claim17, wherein the body further comprises a medial cylindrical aperture inthe medial portion and a lateral cylindrical aperture in the lateralportion, wherein the medial and lateral apertures are configured toreceive pins for insertion into the distal end of the femur to constrainan alignment of the body.
 29. A femoral implant alignment guide,comprising: an elongated resection aperture with a major axissubstantially perpendicular to an axis through a hip center of a patientwhen the femoral implant alignment guide is placed on a distal end of afemur of the patient in alignment with the axis through the hip center;a medial portion comprising a medial tab and configured to contact amedial condyle of the femur when the femoral implant alignment guide isplaced on the distal end of the femur in alignment with the axis throughthe hip center; and a lateral portion comprising a lateral tab andconfigured to contact a lateral condyle of the femur when the femoralimplant alignment guide is placed on the distal end of the femur inalignment with the axis through the hip center, wherein the medial andlateral tabs are configured to constrain a medial-lateral position ofthe femur with respect to the femoral implant alignment guide when thefemoral implant alignment guide is placed on the distal end of the femurin alignment with the axis through the hip center.
 30. The femoralimplant alignment guide of claim 29, wherein the medial and lateralportions are spaced from each other and coupled to a body to define anopening.
 31. The femoral implant alignment guide of claim 29, furthercomprising references located to contact the femur at two or morelocations of the femur, wherein the two or more locations comprise ananterior point on a medial anterior portion of the femur and anotheranterior point on a lateral anterior portion of the femur.
 32. Thefemoral implant alignment guide of claim 29, wherein the femoral implantalignment guide extends around an anterior portion of the medial andlateral condyles toward a posterior portion of the medial and lateralcondyles when the distal end of the femur is received by the femoralimplant alignment guide.
 33. The femoral implant alignment guide ofclaim 29, wherein the femoral implant alignment guide has a connectingportion that connects the medial and lateral portions, wherein themedial and lateral portions each project posteriorly from the connectingportion.
 34. The femoral implant alignment guide of claim 29, furthercomprising a medial anterior portion contact surface and a lateralanterior portion contact surface, wherein the medial and lateralanterior portion contact surfaces are configured to engage an anteriorportion of the medial and lateral condyles, respectively, to restrictanterior displacement of the femoral implant alignment guide withrespect to the femur.
 35. The femoral implant alignment guide of claim29, further comprising a medial aperture in the medial portion and alateral aperture in the lateral portion, wherein the medial and lateralapertures are configured to receive pins for insertion into the distalend of the femur to constrain an alignment of the femoral implantalignment guide.
 36. A femoral implant alignment guide, comprising: abody configured to be placed on a distal end of a femur of a patient inalignment with an axis from between a medial condyle of the femur and alateral condyle of the femur through a hip center of the patient,wherein the body comprises: a medial portion comprising a medial tab anda medial aperture and configured to contact the medial condyle when thebody is placed on the distal end of the femur in alignment with the axisthrough the hip center; and a lateral portion comprising a lateral taband a lateral aperture and configured to contact the lateral condylewhen the body is placed on the distal end of the femur in alignment withthe axis through the hip center, wherein: the medial and lateral tabsare positioned to constrain medial-lateral displacement of the femurwith respect to the body when the body is placed on the distal end ofthe femur in alignment with the axis through the hip center; the medialand lateral portions are spaced apart and project posteriorly from thebody to defines an opening; and the medial and lateral apertures areconfigured to receive pins for insertion into the distal end of thefemur to constrain an alignment of the body.